Re: [PATCH] driver-core: devtmpfs - driver core maintained /dev tmpfs

[Andrew Morton <akpm@linux-foundation.org>]

On Thu, 30 Apr 2009 23:17:01 -0700 Greg KH <greg@kroah.com> wrote:

> On Thu, Apr 30, 2009 at 10:29:00PM -0700, Andrew Morton wrote:
> > On Thu, 30 Apr 2009 15:23:42 +0200 Kay Sievers <kay.sievers@vrfy.org> wrote:
> > 
> > > From: Kay Sievers <kay.sievers@vrfy.org>
> > > Subject: driver-core: devtmpfs - driver core maintained /dev tmpfs
> > > 
> > > Devtmpfs lets the kernel create a tmpfs very early at kernel
> > > initialization, before any driver core device is registered. Every
> > > device with a major/minor will have a device node created in this
> > > tmpfs instance. After the rootfs is mounted by the kernel, the
> > > populated tmpfs is mounted at /dev. In initramfs, it can be moved
> > > to the manually mounted root filesystem before /sbin/init is
> > > executed.
> > 
> > Lol, devfs.
> 
> Well, devfs "done right" with hopefully none of the vfs problems the
> last devfs had. :)

I think Adam Richter's devfs rewrite (which, iirc, was tmpfs-based)
would have fixed up these things.  But it was never quite completed and
came when minds were already made up.

I don't understand why we need devfs2, really.  What problems are
people having with teh existing design?

> > >  block/bsg.c                         |    6 
> > >  drivers/gpu/drm/drm_sysfs.c         |    7 
> > >  drivers/input/input.c               |    6 
> > >  drivers/media/dvb/dvb-core/dvbdev.c |   10 +
> > >  drivers/usb/core/usb.c              |   11 +
> > 
> > These five subsystems were updated, but there are so many others.  Why
> > these five in particular?
> 
> These are the ones that create a subdirectory in /dev/   None of the
> others do.

oic.

Where is it determined that these subsystems create /dev subdirectories? 
udev rules?  If so, do we need to henceforth keep devfs2 (sorry, I
can't resist) in sync with udev?